A gas station's sanitary wastewater, restrooms and any convenience-store use, is designed like any other retail or food-service building and is regulated entirely separately from the site's underground fuel storage tanks, which fall under a different regulatory program altogether.
Underground and aboveground fuel storage tanks are governed by their own state and federal underground storage tank (UST) program, covering leak detection, spill prevention and tank integrity, which has nothing to do with sanitary wastewater design. Keeping these two systems mentally separate matters because they are inspected, permitted and regulated by different authorities with different rules.
The sanitary side, restrooms and any convenience-store food service, is designed the ordinary commercial way: fixture counts for restrooms, plus a food-service calculation and likely grease interception if the store sells prepared food such as hot sandwiches or a deli counter.
A gas station with an attached car wash bay layers that category's oil-water separation and high-volume wash water considerations on top of the ordinary convenience-store design, and should be evaluated the same way a standalone car wash would be.
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A new use, an addition, a remodel, a change of tenant, gets compared against what a commercial property is already permitted for. Where a recorded septic file exists for the property, it typically shows the tank size, the treatment components, the drainfield or dispersal area, and the design flow the system was approved for, which is the starting point for figuring out whether a change fits inside the existing approval or needs an upgrade. We publish where county septic records are kept and how many we hold, we list local septic companies by county, and we generate a free, code-referenced septic design for a parcel to use as a starting point.
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No, fuel storage tanks are regulated under a separate underground storage tank (UST) program covering leak detection and spill prevention, entirely apart from sanitary wastewater design.
It can, if it prepares food such as sandwiches or a deli counter; that triggers the same food-service and grease-interception considerations as a standalone restaurant.
Yes, it adds oil-water separation and high-volume wash water considerations on top of the convenience-store design, the same as a standalone car wash would need.
Page last reviewed 2026-08-31.